G-protein signal transduction pathways are one of the major targets for a vast array of therapeutic drugs and for a variety of compounds that address problems in neurological function. In order to understand how to intervene in an effective way in these ubiquitous and complex pathways we must sort out the function of individual circuits and the mechanisms that cells use to integrate information and to elicit specific responses. We have been characterizing the nature of the protein-protein interactions that mediate information flow in intracellular signaling by generating mutants with specific properties e.g. dominant negative mutants or gene deletions, and correlating their activity in cell culture or in vivo with activity in reconstituted systems. Much of our work has focused on the activity of the various G alpha protein subunits and their effectors. However in the past few years it has become clear that the beta-gamma dimer can interact with a large number of potential effectors including sodium, potassium and calcium channels. In the next grant period we will focus on understanding the function of the beta-gamma dimer particularly as it relates to neuronal activity. We have discovered an interesting gene that encodes a novel beta isoform (beta 5) which is expressed exclusively in neural tissue. We will isolate and characterize the beta 5 gene and compare its structure to that of other beta genes and we will prepare "knockout" mice lacking beta 5 function and study their physiology. We will use site specific and random mutagenesis to define changes in beta-gamma structure that lead to differential interaction with effectors in order to determine the mechanisms that control the wide range of beta gamma activity. We will reintroduce mutants of beta-gamma into specific cells, tissues and animals in order to further define the mechanisms that regulate and integrate G-protein mediated signal transduction.